1. Field of the Invention
This invention relates to an organic electroluminescence device and a method for the manufacturing thereof.
2. Description of Related Art
Recently, an organic electroluminescence display, employing an organic electroluminescence device, referred to below as an organic EL device, is stirring up notice.
An illustrative structure of the organic electroluminescence (EL) display is shown in FIGS. 1 and 2. This organic EL display 20 is comprised of a transparent substrate 21, a plurality of transparent electrodes 22, arranged in stripes, as anode, on the transparent substrate 21, a plurality of organic layers 23, each made up of a positive hole transport layer and a light emitting layer, formed at right angle to the transparent electrodes 22 and a plurality of cathode 24 formed on the organic layers 23, whereby organic EL devices are formed at the intersecting points of the transparent electrodes 22 and the cathodes 24 to form a light emitting area A comprised of a matrix of these organic EL devices, and a contact electrode B is formed in the vicinity of the light emitting area A for taking out the light emitting area to an external circuit or to an inner driving circuit.
Although not shown, an insulating layer is usually provided between the neighboring transparent electrodes 22, whereby the shorting across neighboring transparent electrodes 22 and that across the transparent electrodes 22 and the cathodes 24 may be prevented from occurring.
In such organic EL display, there is, for example, a single hetero type organic EL device 30, shown in FIG. 16, as an organic EL device constructed at an intersection of the transparent electrode 22 and the cathode 24. This organic EL device 30 includes a transparent substrate 21, such as a glass substrate, on which there are sequentially formed an anode of, for example, ITO (indium tin oxide), an organic layer 23, made up of a positive hole transport layer 23a and a light emitting layer 23b, and a cathode 24, arranged in this order.
If, in the above-described organic EL device 30, a positive voltage and a negative voltage are applied to the anode and cathode, the positive holes implanted from the anodes reach the light emitting layer 23b through the positive hole transport layer 23a, whilst the electrons implanted at the cathode reach the light emitting layer 23b, so that electron-positive hole recombination occurs in the light emitting layer 23b. The light of a pre-set wavelength is emitted at this time and radiated from the transparent substrate 21 side to outside as indicated by arrow in FIG.3.
However, an organic fluorescent solid material, as a material of the light emitting layer of the organic EL device, is vulnerable to moisture or to oxygen, whilst the cathode provided on the light emitting layer tends to be deteriorated in characteristics due to oxidation. Thus, if the conventional organic EL device is driven in atmospheric air, it is rapidly deteriorated in light emitting characteristics to form a dark point not emitting the light. Thus, in order to realize a practically useful organic EL device or organic EL display, the device needs to be sealed to elongate its service life to prevent intrusion of moisture or oxygen into the organic layer as well as to prevent oxidation of the counter-electrodes.
As a method for sealing the device, there has so far been proposed a method of annexing a de-oxidation agent, such as barium oxide, in a metal cap, on the reverse side of the organic EL device display, to seal dry nitrogen. However, this method complicates the process for sealing the device to raise production difficulties.
Moreover, since a driving circuit is mounted in the vicinity of the display device in the conventional passive matrix system, difficulties are met in the conventional passive matrix system in increasing the screen size due to, for example, voltage drop caused by wiring resistance of the driving circuit.
It is therefore an object of the present invention to provide an organic EL devices which may be sealed readily and which permits the display employing the device to be increased in size, and a method for the manufacturing of the organic EL device.
In one aspect, the present invention provides an organic electroluminescence device includes a transparent substrate, an electrode film formed on the transparent substrate, a transparent electrode film formed on the electrode film, a first insulating film formed on the transparent electrode film and having an opening over the transparent electrode film, an organic electroluminescence light emitting film formed over a portion of the transparent electrode film exposed from the opening in the first insulating film, the organic electroluminescence light emitting film being larger in size than the opening and being formed over the first insulating film, a metal electrode film formed on the organic electroluminescence light emitting film and a second insulating film formed on the metal electrode film so as to be larger in size than both the organic electroluminescence light emitting film and the metal electrode film.
In the organic electroluminescence device according to the present invention, the first and second insulating films exhibit gas barrier characteristics, and the opening is tapered so that its opening degree is increased in a direction away from the transparent electrode film side. The transparent electrode film is electrically connected through the electrode film to a first electrode passed through the first and second insulating films so as to be exposed on the second insulating film. The metal electrode film is electrically connected to a second electrode passed through the second insulating film so as to be exposed on the second insulating film.
In the organic electroluminescence device according to the present invention, in which the first and second insulating films exhibit gas barrier characteristics, it is possible to prevent intrusion of moisture or oxygen into the inside of the device, by a simplified structure, without sealing the device. Moreover, in the present organic electroluminescence device, in which the first and second electrodes are exposed on a device surface opposite to the transparent substrate, the driving circuit substrate for driving the substrate can be arranged on the back side of the device.
In another aspect, the present invention provides a method for the manufacturing of an organic electroluminescence device including an electrode film forming step of forming an electrode film on a transparent substrate, a transparent electrode film forming step of forming a transparent electrode film on the electrode film, a first insulating film forming step of forming a first insulating film exhibiting gas barrier characteristics on the transparent electrode film, an opening forming step of forming an opening in the first insulating film for exposing a portion of the transparent electrode film, a step of forming an organic electroluminescence light emitting film on the portion of the transparent electrode film exposed from the opening in the first insulating film so that the organic electroluminescence light emitting film will be extended over the first insulating film to a size larger than that of the opening, a metal electrode film forming step of forming a metal electrode film on the organic electroluminescence light emitting film, a second insulating film forming step of forming a second insulating film exhibiting gas barrier characteristics so that the second insulating film will be extended over the metal electrode film to a size larger than that of both the organic electroluminescence light emitting film and the metal electrode film, a first electrode forming step of forming a first electrode so that the first electrode is passed through the first and second insulating films so as to be exposed on the second insulating film and electrically connecting the first electrode to the transparent electrode film through the electrode film, a second electrode forming step of forming a second electrode so that the second electrode is passed through the second insulating film so as to be exposed on the second insulating film and electrically connecting the second electrode to the metal electrode film and a driving circuit connecting step of connecting a driving circuit to the first electrode and/or to the second electrode and mounting the driving circuit on an electrode electrically connected to the driving circuit. In the opening forming step, the opening is formed so that its opening degree is larger in a direction away from the transparent electrode film side.
In the method for the manufacturing of the organic electroluminescence device according to the present invention, since the first and second insulating films exhibiting gas barrier characteristics are used, a device in which moisture or oxygen is prevented from being intruded into the inside of the device may be prepared by a simplified structure, without sealing the device. Moreover, in the present method, since the first and second electrodes are exposed on a device surface opposite to the transparent substrate, the driving circuit substrate for driving the substrate can be arranged on the back side of the device.
According to the present invention, an organic electroluminescence device can be prepared and sealed more readily than in the conventional system. Since the organic electroluminescence device can be prepared without using metal caps, de-oxidation agents or dry nitrogen, the manufacturing device may be simplified, at the same time as integrated production in vacuum may be achieved.
In addition, since the electrodes for driving the organic electroluminescence device may be taken out from the back side, the device may be integrated to a high density.